Bleaching powder is correctly represented as

Which of the following statements is incorrect?

Thermal stability of $BaCO_3, CaCO_3, SrCO_3$ and $MgCO_3$ decreases in the order of :

Slaked lime is used in the manufacture of

The solubility of sulfates in water decreases down the group for $Be$ to $Ba$. The correct order is $BeSO_4 > MgSO_4 > CaSO_4 > SrSO_4 > BaSO_4$. The reason for this is:

$BeO$ reacts with $HF$ in the presence of ammonia to give $[A]$,which on thermal decomposition produces $[B]$ and ammonium fluoride. The oxidation state of $Be$ in $[A]$ is $.....$.